Examples...Digital topography...


Simulating Galileo's Views


Description


The original purpose of LTVT was to compare certain undated lunar drawings attributed to Galileo Galilei to what might have been seen by him on various nights in 1609-1610; with the intent of seeing if any convincing matches could be made to particular nights. This can be done either by attempting to find photos of the Moon taken under the same circumstances, or by simulating what the Moon should have looked like using digital elevation models.

The latter approach has the advantage that any date or time can be recreated at the touch of a button, but only recently have accurate enough models for doing this become available. The Kaguya global DEM at a resolution of 16 points per degree shows some promise, at least for illustrating the pattern of light and shadow expected to be seen along the terminator at full disk scale. The following are preliminary simulations generated by LTVT base on it, showing what Galileo should have been able to seen during night-time hours (Sun below horizon) with the Moon visible (above horizon).

All views are from Padua, Italy. These do not include the albedo variations that give the main sunlit portion of the lunar disk much of its character.

Specific Dates

Click on the thumbnails to see the full-sized LTVT screenshots.

1609 Nov 28

Here is what Galileo could have been seen in the brief interval from sunset to moonset on of the first nights of this lunation
15:30 UT
17:00 UT
external image LTVT_Galileo_1609Nov28_1530UT.jpg?size=64
external image LTVT_Galileo_1609Nov28_1700UT.jpg?size=64

1609 Nov 29

...and the following evening
15:30 UT
17:50 UT
external image LTVT_Galileo_1609Nov29_1530UT.jpg?size=64
external image LTVT_Galileo_1609Nov29_1750UT.jpg?size=64

1609 Nov 30

This is what Ewen Whitaker believes was the date of what he thinks were Galileo's first lunar observations -- those involving a triangular peak emerging into sunlight on what we now call the southeast terminator. The simulations show what Galileo could have been seen from sunset to moonset on Whitaker's date.
15:00 UT
19:00 UT
external image LTVT_Galileo_1609Nov30_1500UT.jpg?size=64
external image LTVT_Galileo_1609Nov30_1900UT.jpg?size=64

1609 Dec 01

Here is what Galileo could have been seen from sunset to moonset the following night.
15:30 UT
16:30 UT
19:30 UT
external image LTVT_Galileo_1609Dec01_1530UT.jpg?size=64
external image LTVT_Galileo_1609Dec01_1630UT.jpg?size=64
external image LTVT_Galileo_1609Dec01_1930UT.jpg?size=64

1609 Dec 02

...and the one after that.
15:30 UT
20:30 UT
external image LTVT_Galileo_1609Dec02_1530UT.jpg?size=64
external image LTVT_Galileo_1609Dec02_2030UT.jpg?size=64


1610 Jan 19

On this date Ewen Whitaker believes Galileo made a drawing of a star emerging from occultation at around 05:50 UT. Here is what Galileo could have seen from moonrise to sunrise.
02:00 UT
05:50 UT
07:00 UT
external image LTVT_Galileo_1610Jan19_0200UT.jpg?size=64
external image LTVT_Galileo_1610Jan19_0550UT.jpg?size=64
external image LTVT_Galileo_1610Jan19_0700UT.jpg?size=64

All the preceding simulations are reproduced with a "gamma" of 2 to reproduce brightness levels more "realistically" on a computer screen. Here is the 1610 Jan 19 05:50 UT scene as it appears with gamma of 1:
external image LTVT_Galileo_1610Jan19_0550UT_Gamma_1.jpg?size=64



This page has been edited 5 times. The last modification was made by - JimMosher JimMosher on Nov 28, 2009 12:44 pm